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what's the difference between using an ordinary pointer and a "pointer to member"?

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what's the difference between using an ordinary pointer and a "pointer to member"?

 
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  #1
Nov 23rd, 2008
C++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. using namespace std;
  3. #define PRINT(x) cout << #x " = " << x << endl;
  4.  
  5. class Object{
  6. public:
  7. 	Object():i(5){}
  8. 	 int i;;
  9. };
  10.  
  11. int main() {
  12. 	Object o;
  13. 	o.i = 5;
  14. 	int* p = &(o.i);
  15. 	PRINT(*p);
  16.  
  17. 	int Object::* p2m = &Object::i;
  18. 	PRINT(o.*p2m);
  19. 	return 0;
  20. }

the two PRINT macros produce this:
C++ Syntax (Toggle Plain Text) 
  1. *p = 5
  2. o.*p2m = 5

could you tell me what the difference is between using them? when should i choose one over another? and why?
Thank you in advance!
Last edited by Ancient Dragon; Nov 23rd, 2008 at 10:16 pm. Reason: replaced quote tags with code tags
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Re: what's the difference between using an ordinary pointer and a "pointer to member"?

 
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  #2
Nov 24th, 2008
Well ordinarily, your data in the class wouldn't be public to begin with.

Making it public defeats the whole purpose of having classes at all.
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Re: what's the difference between using an ordinary pointer and a "pointer to member"?

 
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  #3
Nov 24th, 2008
Read about:
- pointers to member functions:
http://www.gidforums.com/t-18332.html
- pointer to data members:
http://www.icce.rug.nl/documents/cpl...us15.html#l219
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